Component Snapshot At-a-Glance
- Model: A2H254-16
- Alt. P/N: Foxboro OEM branded part number P0973BK
- Product Series: Enterasys SecureStack A2 Managed Industrial Switch Series
- Hardware Type: 1U 19-inch rackmount Layer2+ stackable mixed media managed switch
- Key Feature: Split 8×RJ45 copper +8×MT-RJ 100BASE-FX fixed ports plus dual Gigabit SFP uplink slots
- Primary Field Use: Terminate mixed copper field instruments and multimode fiber Foxboro FBM I/O inside DCS process cabinets.
ENTERASYS A2H254-16
Hard-Numbers: Technical Specifications
- Protocol Support: 802.1Q VLAN, RSTP/MSTP, 802.1p QoS, LACP, IGMP Snooping, SNMPv2c, Port ACL
- Port Count: 8×10/100TX RJ45,8×100BASE-FX MT-RJ,2×Gigabit RJ45 stack ports,2×Gigabit SFP slots,1×DB9 RS232 Console
- Baud/Data Rate: 10/100Mbps auto-negotiate copper; fixed 100Mbps multimode fiber; 10/100/1000Mbps SFP uplink
- Operating Temperature: 0°C to +50°C continuous in closed cabinet; -40°C to +70°C warehouse non-operating storage
- Isolation Rating: 1500VAC isolation between front fiber transceiver bank and main switching PCB for MCC surge suppression
- Power Draw: Max 29W full rated operating load
- Switch Fabric: 32Gbps switching capacity; 23.8Mpps wire-speed forwarding throughput
- MAC Table Depth: 16384 address entries stored on non-volatile onboard flash
- Input Power: Universal 100–240VAC 50/60Hz internal PSU, compatible with external C2RPS-PSM redundant backup supply
The Real-World Problem It Solves
Mixed-signal DCS racks force techs to stack standalone copper switches and separate fiber media converters, eating critical cabinet rack space and multiplying spare part inventories site-wide. Copper cabling near high-current MCC bus bars picks heavy EMI noise, triggering random FBM I/O dropouts and floating process variable readings mid-run.
Where you’ll typically find it:
- Refinery CDU/FCC remote I/O cabinets combining local panel instruments (copper) and distant field FBM modules (multimode fiber)
- Coal-fired power boiler auxiliary DCS racks tying local PLCs via RJ45 and feedwater field controllers via MT-RJ fiber
- Outdoor chemical process shelters needing mixed copper/fiber termination to bypass CAT5’s 100m distance cap
This single chassis eliminates extra media converters and consolidates mixed media termination to cut cabinet clutter and EMI-induced intermittent communications faults.
Hardware Architecture & Under-the-Hood Logic
This unit uses electrically split dual PCB layout; fiber transceiver daughterboard stays galvanically separated from main ASIC/CPU board to block cabinet voltage spikes from frying core switch logic. It sits on the DCS edge tier between field I/O hardware and core plant backbone switches.
- Inbound copper Ethernet from local instruments lands on RJ45 PHY chips; incoming optical fiber signals convert to electrical via fixed MT-RJ multimode transceivers.
- All converted frames feed into central Layer2 switching ASIC for header parsing and queue assignment per preloaded Foxboro DCS QoS rules.
- Control-class Modbus and proprietary DCS traffic locks into highest priority transmit queue above historian bulk data to avoid forwarding delays.
- Local I/O-to-I/O traffic switches across internal fabric; uplink bound packets route out either dedicated RJ45 stack ports or available SFP gigabit slots.
- Stack protocol syncs configuration and firmware across chained A2 units to operate as one unified logical switching domain.
- Onboard flash memory saves startup-config through full AC power loss to avoid manual reconfiguration after cabinet power blips.
ENTERASYS A2H254-16
Field Service Pitfalls: What Rookies Get Wrong
Mismatched SFP Transceiver Types in Gigabit Uplink SlotsNew field crews plug single-mode LX SFPs into uplink slots and pair with site-installed multimode fiber runs. Wavelength mismatch creates erratic uplink flapping and random DCS PV dropouts during temperature swings.
- Quick Fix: Restrict uplink transceivers exclusively to 850nm SX multimode SFP matching OEM Foxboro field specifications.
Improper Redundant Power Supply Model SelectionTechs hook up POE-rated C2RPS-POE instead of specified C2RPS-PSM backup supply; excess POE voltage feed damages internal regulator IC and can permanently short the mainboard.
- Field Rule: Only pair with non-POE C2RPS-PSM external redundant power modules for backup failover.
Stacking Units With Unsynchronized Firmware RevisionsWorkers add spare replacement directly into live stack without cross-checking firmware build numbers. Version mismatch triggers stack split and isolates the newly added switch with all ports non-functional.
- Quick Fix: Bench test spare hardware offline, upgrade/downgrade firmware to match existing stack master revision before stacking cable installation into live DCS network.
Commercial Availability & Pricing Note
Please note: The listed price is for reference only and is not binding. Final pricing and terms are subject to negotiation based on current market conditions and availability.
